SUNRPC: drop unused xs_reclassify_socketX() helpers

xs_reclassify_socket4() and friends used to be called directly.
xs_reclassify_socket() is called instead nowadays.

The xs_reclassify_socketX() helper functions are empty when
CONFIG_DEBUG_LOCK_ALLOC is not defined.  Drop them since they have no
callers.

Note that AF_LOCAL still calls xs_reclassify_socketu() directly but is
easily converted to generic xs_reclassify_socket().

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>